Browsing by Author "An, Q."
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Item Branching Fraction Measurements of ψ(3686) → γχ_{cj}(2018-05-24) Ablikim, M.; Achasov, M. N.; Albrecht, M.; Ahmed, S.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouUsing a sample of 106 million ψ(3686) decays, the branching fractions of ψ(3686) → γχ_{c0}, ψ(3686) → γχ_{c1}, and ψ(3686) → γχ_{c2} are measured with improved precision to be (9.389 ± 0.014 ± 0.332) %, (9.905 ± 0.011 ± 0.353) %, and (9.621 ± 0.013 ± 0.272) %, respectively, where the first uncertainties are statistical and the second ones are systematic. The product branching fractions of ψ(3686) → γχ_{c1}, χ_{c1} → γJ/ψ and ψ(3686) → γχ_{c2}, χ_{c2} → γJ/ψ and the branching fractions of χ_{c1} → γJ/ψ and χ_{c2} → γJ/ψ are also presented.Item Determination of the Number of ψ(3686) Events at BESIII(Chinese Physical Soc) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Olsen, S. L.; BESIII Collaboration; Olsen, S. L.The numbers of ψ(3686) events accumulated by the BESIII detector for the data taken during 2009 and 2012 are determined to be (107.0 ± 0.8) x10⁶ and (341.1 ± 2.1) x10⁶, respectively, by counting inclusive hadronic events, where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is (448.1 ± 2.9) x 10⁶.Item Improved Measurements of Two-Photon Widths of The χ(cJ) States and Helicity Analysis For χ(c2) → γγ(Amer Physical Soc, 2018-10-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouBased on 448.1 x 10⁶ ψ(3686) events collected with the BESIII detector, the decays ψ(3686) → γ χ(cJ), χ(cJ) → γγ(J = 0, 1, 2) are studied. The decay branching fractions of χ(c0,2) → γγ are measured to be ℬ(χ(c0) → γγ) = (1.93 ± 0.08 ± 0.05 ± 0.05) x 10⁻⁴ and ℬ(χ(c2) → γγ) = (3.10 ± 0.09 ± 0.07 ± 0.11) x 10⁻⁴ which correspond to two-photon decay widths of Γ(γγ)(χ(c0)) = 2.03 ± 0.08 ± 0.06 ± 0.13 keV and Γ(γγ)(χ(c2)) = 0.60 ± 0.02 ± 0.01 ± 0.04 keV with a ratio of R = Γ(γγ)(χ(c2))/Γ(γγ)(χ(c0)) = 0.295 ± 0.014 ± 0.007 ± 0.027, where the uncertainties are statistical, systematic and associated with the uncertainties of ℬ(ψ(3686) → γχ(c2)) and the total widths Γχ(c0,2), respectively. For the forbidden decay of χ(c1) → γγ, no signal is observed, and an upper limit on the two-photon width is obtained to be Γ(γγ)(χ(c1)) < 5.3 eV at the 90% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay χ(c2) → γγ is also measured to be f(0/2) = Γ(γγ)(λ=0) (χ(c2)) / Γ(γγ)(λ=2) (χ(c2) = (0.0 ± 0.6 ± 1.2) x 10(-2), where the uncertainties are statistical and systematic, respectively.Item Measurements of the Branching Fractions for the Semileptonic Decays D(s)⁺ → φe⁺ν(e), φμ⁺ν(μ), ημ⁺ν(μ) and η′μ⁺ν(μ)(Amer Physical Soc, 2018-10-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouBy analyzing 482 pb⁻¹ of e⁺e⁻ collision data collected at the center-of-mass energy √s = 4.009 GeV with the BESIII detector, we measure the branching fractions for the semi-leptonic decays D(s)⁺ → φe⁺ν(e), φμ⁺ν(μ), ημ⁺ν(μ) and η′μ⁺ν(μ) to be ℬ(D(s)⁺ → φe⁺ν(e)) = (2.26 ± 0.45 ± 0.09)%, ℬ(D(s)⁺ → φμ⁺ν(μ)) = (1.94 ± 0.53 ± 0.09)%, ℬ(D(s)⁺ → ημ⁺ν(μ)) = (2.42 ± 0.46 ± 011)% and ℬ(D(s)⁺ → η′μ⁺ν(μ)) = (1.06 ± 0.54 ± 0.07)%, where the first and second uncertainties are statistical and systematic, respectively. The branching fractions for the three semi-muonic decays D(s)⁺ → φμ⁺ν(μ), ημ⁺ν(μ) and η′μ⁺ν(μ) are determined for the first time and that of D(s)⁺ → φe⁺ν(e) is consistent with the world average value within uncertainties.Item Observation of a Charged Charmoniumlike Structure in e⁺e⁻ → (D*D̅*)^± π^∓ at √s=4.26 GeV(American Physical Society, 2014-04-02) Ablikim, M.; Achasov, M. N.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Bai, J. Z.; Lou, Xinchou; Lou, XinchouWe study the process e⁺e⁻ → (D*D̅*)^± π^∓ at a center-of-mass energy of 4.26 GeV using a 827 pb⁻¹ data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be (137 ± 9 ± 15) pb. We observe a structure near the (D*D̅*)^± threshold in the π^∓ recoil mass spectrum, which we denote as the Z_c ^±(4025). The measured mass and width of the structure are (4026.3 ± 2.6 ± 3.7) MeV/c² and (24.8 ± 5.6 ± 7.7) MeV, respectively. Its production ratio σ(e⁺ e⁻ → Z_c ^±(4025)π^∓ → (D*D̅*)^± π^∓ / σ(e⁺ e⁻ → ((D*D̅*)^± π^∓ is determined to be 0.65 ± 0.09 ± 0.06. The first uncertainties are statistical and the second are systematic.Item Observation of e⁺e⁻ → γX(3872) at BESIII(2014-03-03) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Lou, Xinchou; Lou, XinchouWith data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process e⁺e⁻ → γ X(3872) is observed for the first time with a statistical significance of 6.3σ. The measured mass of the X(3872) is (3871.9 ± 0.7(stat) ± 0.2(syst)) MeV/c², in agreement with previous measurements. Measurements of the product of the cross section σ[e⁺e⁻ → γ X(3872)] and the branching fraction ℬ [X(3872) → π⁺π⁻J/ψ] at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process Y(4260) → γ X(3872).Item Observation of the Decay Λ_c⁺→ Σ⁻π⁺π⁺π⁰(Elsevier B.V, 2017) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); Lou, XinchouWe report the first observation of the decay Λ_c⁺→ Σ⁻π⁺π⁺π⁰, based on data obtained in e⁺e⁻ annihilations with an integrated luminosity of 567 pb⁻¹ at √s̅=4.6 GeV. The data were collected with the BESIII detector at the BEPCII storage rings. The absolute branching fraction B(Λ_c⁺ → Σ⁻π⁺π⁺π⁰ is determined to be (2.11 ± 0.33(stat.) ± 0.14(syst.))%. In addition, an improved measurement of B( Λ_c⁺→ Σ⁻π⁺π⁺) is determined as (1.81 ± 0.17(stat.) ± 0.09(syst.))%.Item Precision Measurements of B(D⁺ → μ⁺ν_μ), the Pseudoscalar Decay Constant ʄ_D⁺ and the Quark Mixing Matrix Element |V_{cd}|(Amer Physical Soc, 2014-03) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Lou, Xinchou; Lou, XinchouWe report a measurement of the branching fraction B(D⁺ → μ⁺ν_μ) = [3.71 ± 0.19(stat) ± 0.06(sys)] x 10⁻⁴ based on 2.92 fb⁻¹ of data accumulated at √s = 3.773 GeV with the BESIII detector at the BEPCII collider. This measurement, in conjunction with the Cabibbo-Kobayashi-Maskawa matrix element |V_{cd}| determined from a global Standard Model fit, implies a value for the weak decay constant ʄ_{D⁺} = (203.2 ± 5.3 ± 1.8) MeV. Additionally, using this branching fraction measurement together with a lattice QCD prediction for ʄ_{D⁺}, we find |V_{cd}| = 0.2210 ± 0.0058 ± 0.0047. In either case, these are the most precise results for these quantities to date.